Heat collector with mounting plate

ABSTRACT

A heat collector ( 50 ) is formed by at least one extruding step for reducing machining steps, and is assembled to a separately formed mounting frame ( 40 ) which may be stamped and formed or molded. The heat collector has flanges ( 53 ) which bear against retaining tabs ( 45 ) formed on the mounting frame, and may be held by solder, glue, or mechanical means. The heat collector may receive a heat dissipator ( 18 ), or may be formed as a heat sink ( 56 ) such as a pin-fin type heat sink. The mounting frame can be fixed to a printed circuit board or the like having a component such as a central processing unit which contacts the collector in order to cool the unit.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a heat sink for cooling anelectronic device mounted to a printed circuit board, and in particularto a surface mounted collector plate which is in direct thermal contactwith a CPU.

[0003] 2. Description of the Related Art

[0004] The current collector plate incorporates features for mounting toa printed circuit board, thermal contact with a CPU and heat spreading,and connection to a heat pipe all in a single part. This requiresmultiple machining steps and plating on a monolithic part.

[0005] Referring to FIGS. 1A and 1B, a CPU 12 is mounted to a PCB 10which is provided with studs 14 for mounting a heat collector 20including a mounting plate 25 having tabs 22 and holes 23 for receivingthe studs 14. The collector 20 is also provided with parallel ridges 24defining a central channel 26 which receives a heat pipe 16 connected toa heat dissipator 18 having cooling fins. It is partially filled withliquid which undergoes a cycle of condensation and evaporation betweenthe collector 20 and the heat dissipator 18. The pipe may be received inthe channel in a press-fit, or it may be soldered or held by thermallyconductive bonding, whereupon a cover plate 28 is soldered or bonded inplace to improve heat transfer. The pipe 16 is shown having a closedend, buy may also be part of a conventional cooling loop.

[0006]FIGS. 2A to 2C show the steps which are necessary to produce theunitary heat collector 20 and mounting plate 20 according to the priorart. FIG. 2A shows a machined or extruded block of metal 21 having apair of ridges 24 upstanding from a plate 25 and flanking a centralchannel 26, and an inset 27 for receiving a cover plate. Whether theblock is machined or extruded depends on the material; copper is not asreadily extruded as aluminum. The material chosen depends on the desiredproperties such as cost, weight, thermal conductivity, extrudability,and solderability. The block of FIG. 2A is milled to enlarge the baseplate 25 at both ends of the ridges 24 (FIG. 2B) . The plate 25 is thenmilled to form the tabs 23 and drilled to form the holes (FIG. 2C).

[0007]FIG. 3A shows the first step in producing a unitary pin fin typeheat sink according to the prior art, wherein a plate 32 havingupstanding ribs 33 is extruded. FIG. 3B shows the second step, whereinthe ribs are machined or gang-sawed to produce pins 34. As shown in FIG.3C, the plate is then machined to produce tabs 36, and the tabs aredrilled to produce holes 38.

SUMMARY OF THE INVENTION

[0008] According to the invention, the attachment/alignment features areseparated from the thermal features, thereby reducing production costsby eliminating multiple machining steps. The heat collector according tothe invention includes two parts, a block to collect heat from a CPU orthe like, and a molded or stamped frame that surrounds and locates theblock and also provides mounting features such as bosses for screws,bolts, rivets, push-pins or the like.

[0009] The invention is based on the realization that the heatcollecting and dissipating function is independent of the mounting andlocating function, whereby the functions may be assumed by separateparts which are collectively less expensive to manufacture than a singlepart, which typically requires numerous machining steps. The inventionalso permits using any number of heat collector configurations with thesame mounting plate.

[0010] The metal heat collector may be an extrusion, plated (ifrequired) as one part and cut to length. This is preferable for aheat-pipe type heat collector or a fin type heat sink. Pin fin type heatsinks as depicted in the figures require some machining after extrusion.Note that the term “heat collector” as used herein refers to an elementwhich “collects” the heat from a source such as a chip, and eitherdissipates the heat or transfers it by a pipe or the like to a remoteheat dissipator. The term “heat sink” as used herein refers to anelement which not only collects the heat, but performs the dissipatingfunction. Thus a heat sink is a species of collector.

[0011] The mounting frame may be molded of plastic, thereby eliminatingall machining and drilling. Plastic may be molded of metal filledmaterial for EMI shielding. The plastic may be highly heat resistant sothat the heat pipe can be soldered to the heat sink after assembly.

[0012] The mounting frame may also be stamped and formed of metal, whichwould not only eliminate machining and drilling, but would also aid inheat dissipation. Similar parts could be made of spring steels andincorporate springs for heat sink attachment to PCB's. Where both partsare metal, several methods including soldering, swaging, staking,brazing, bonding, welding and spot welding can be used to join theparts.

[0013] Other objects and features of the present invention will becomeapparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are designed solely for purposes ofillustration and not as a definition of the limits of the invention, forwhich reference should be made to the appended claims. It should befurther understood that the drawings are not necessarily drawn to scaleand that, unless otherwise indicated, they are merely intended toconceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1A is an exploded perspective of a prior art heat pipe typeheat collector assembly and a printed circuit board;

[0015]FIG. 1B is a perspective of the prior art heat collector assemblyas assembled to a printed circuit board;

[0016]FIGS. 2A-2C show manufacturing steps of a prior art heat collectorfor a heat pipe;

[0017]FIGS. 3A-3C show manufacturing steps of a prior art pin fin typeheat sink with mounting tabs;

[0018]FIG. 4A is an exploded perspective of a two-part heat collectoraccording to the invention;

[0019]FIG. 4B is a perspective of an assembled two-part heat collectoraccording to the invention;

[0020]FIG. 5 is a perspective of a heat collector having multiplechannels for receiving heat pipes;

[0021]FIG. 6 is a perspective of a system having a single heat collectorconnected to multiple heat dissipators;

[0022]FIG. 7A is an exploded perspective of a first embodiment of a twopart pin fin type heat sink according to the invention;

[0023]FIG. 7B is a perspective of an assembled two-part pin fin typeheat sink of FIG. 6A;

[0024]FIG. 8A is an exploded perspective of a second embodiment of a twopart pin fin type heat sink according to the invention;

[0025]FIG. 8B is a perspective of an assembled two-part pin fin typeheat sink of FIG. 7A;

[0026]FIG. 9 is a perspective of a third embodiment of a two-part pinfin type heat sink, as assembled;

[0027]FIG. 10 is a perspective of a fourth embodiment of a two-part pinfin type heat sink, as assembled, and

[0028]FIG. 11 is a perspective of a fifth embodiment of a two-part pinfin type heat sink, as assembled.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0029] Referring to FIGS. 4A and 4B, the mounting frame 40 is stampedand formed of metal plate such as aluminum and includes mounting tabs 42having holes 43, a central aperture 44, and retaining tabs 45 formed toextend above a plane containing the mounting tabs 42. The heat collector50 is profiled for close reception in the central aperture 44 of themounting frame 40, and has side flanges 53 which bear against retainingtabs 45. Parallel ridges 51 define a channel 52 which receives the heatpipe, the collector 50 preferably being extruded copper in order tofacilitate soldering to a copper heat pipe. Note that soldering of theretaining plate 40 to the collector 50 is not necessary, but is possiblewhere both parts are solder-compatible, thereby further improving heatdissipation.

[0030]FIG. 5 shows a heat collector having multiple channels 26 forconnecting multiple heat pipes to multiple dissipators in applicationswhich require a high heat transfer. Conversely, discrete heat collectorshaving single channels may be connected to a single heat dissipator 18by discrete heat pipes 16, as shown in FIG. 6.

[0031]FIGS. 7A and 7B show a mounting plate 40 which is substantiallyidentical to the mounting plate in FIGS. 4A and 4B, and may likewise beeither molded plastic or stamped and formed metal. Here a pin fin typeheat sink 56 is provided with flanges 57 for retention by the retainingtabs 42 of the mounting plate. The heat sink 56 may be manufactured byextruding to form parallel fins, then gang sawing transversely to thefins to form fins 50, as described in U.S. Pat. No. 4,884,331.

[0032]FIGS. 8A and 8B show an embodiment similar to that of FIGS. 7A and7B, wherein the retaining tabs 45 are provided with comb-like springteeth 46 which fit between columns of pins 58. Where both parts are madeof metal, this arrangement can improve thermal contact without solder,whereby one or both of the parts may be aluminum.

[0033]FIG. 9 shows an embodiment wherein the mounting plate 40 is formedwith upwardly extending retaining tabs 47 which are attached to the heatcollector by rivets 48 fitted through holes (not visible) and wedgedbetween pins 58.

[0034]FIG. 10 shows an embodiment wherein upwardly extending tabs 48engage against detents 59 formed on outside rows of pins 58, therebyretaining the heat sink 50 to the mounting plate 40 in a snap-fit.

[0035]FIG. 11 shows a pin fin type heat sink 56 having flanges 57 (FIG.6A) which are held against the underside of a stamped retaining plate 40which does not have formed tabs. Here the bottom of the heat sink is notflush with the bottom of the mounting plate 40, whereby the mountingplate 40 will be spaced from the PCB when mounted.

[0036] Note that other described embodiments having retaining tabs 45may be designed so the bottom of the heat sink is recessed in themounting plate, whereby the mounting plate may be mounted flushlyagainst the PCB while a CPU upstanding from the PCB is flush against thebottom of the heat sink.

[0037] Thus, while there have shown and described and pointed outfundamental novel features of the invention as applied to a preferredembodiment thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of the devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit of the invention. For example, itis expressly intended that all combinations of those elements and/ormethod steps which perform substantially the same function insubstantially the same way to achieve the same results are within thescope of the invention. Moreover, it should be recognized thatstructures and/or elements and/or method steps shown and/or described inconnection with any disclosed form or embodiment of the invention may beincorporated in any other disclosed or described or suggested form orembodiment as a general matter of design choice. It is the intention,therefore, to be limited only as indicated by the scope of the claimsappended hereto.

What is claimed is:
 1. A heat collector assembly comprising: a heatcollector which can be fitted against a component to be cooled, saidheat collector having two opposed lateral flanges, and a mounting frameformed separately from said heat collector and fitted thereto, saidmounting frame having a central aperture which receives said heatcollector, and retaining means which bear against said flanges toposition said heat collector with respect to said mounting frame.
 2. Aheat collector as in claim 1 wherein said mounting frame is asubstantially planar plate.
 3. A heat collector as in claim 2 whereinsaid retaining means comprise retaining tabs extending above the planeof the plate.
 4. A heat collector as in claim 1 wherein said mountingframe is stamped and formed of metal.
 5. A heat collector as in claim 1wherein said mounting frame is molded of plastic.
 6. A heat collector asin claim 1 wherein said heat collector is formed with a channel forreceiving a heat pipe.
 7. A heat collector as in claim 6 wherein saidheat collector is formed with a pair of parallel ridges flanking saidchannel, said flanges flanking said ridges.
 8. A heat collector as inclaim 6 wherein said heat collector is formed with a plurality of saidchannels in parallel for receiving a respective plurality of heat pipes.9. A heat collector as in claim 6 wherein said heat collector is anextruded piece.
 10. A heat collector as in claim 1 wherein said mountingframe is stamped and formed of metal.
 11. A heat collector as in claim 1wherein said mounting frame is molded of plastic.
 12. A heat collectoras in claim 1 wherein said heat collector is a pin fin type heat sinkhaving rows of pins parallel to said flanges.
 13. A heat collector as inclaim 12 wherein said retaining means comprise retaining tabs havingcomb-like teeth which extend between pins in rows adjacent to saidflanges.
 14. A heat collector as in claim 12 wherein said retainingmeans comprise tabs which are formed upward and bear against respectiverows of pins which are adjacent to said flanges.
 15. A heat collector asin claim 14 wherein said pins in rows next to said flanges have distalends formed with detents which lock against distal ends of said upwardformed tabs.
 16. A heat collector as in claim 14 wherein said upwardformed tabs have respective holes, said heat collector furthercomprising rivets extending through said holes and between respectivepairs of pins.
 17. A heat dissipating system comprising a plurality ofheat collector assemblies which can be fitted against components to becooled, a heat dissipating unit, a plurality of pipes for transferringheat from respective said heat collectors to said heat dissipating unit.18. A heat dissipating system as in claim 17 wherein said pipes carry acooling medium.
 19. A heat dissipating system as in claim 18 whereinsaid pipes are heat pipes.
 20. A heat dissipating system as in claim 17wherein each said heat collector has two opposed lateral flanges, eachsaid heat collector assembly further comprising a mounting frame formedseparately from said heat collector and fitted thereto, said mountingframe having a central aperture which receives said heat collector, andretaining means which bear against said flanges to position said heatcollector with respect to said mounting frame.